Apparatus for automatically differentiating and feeding flexible workpieces one at a time from a stack

ABSTRACT

A hopper holds a stack of workpieces which are fed to a discharge mouth at one end of the hopper by intermittent pressure feed means, a movable suction head located near the discharge mouth, through which suction is applied, withdraws the end pieces, one at a time, from the stack away from the discharge mouth (at time intervals) during cycles of operation when the intermittent feed means relieves the pressure applied to the stack.

ite States Patent Inventor Herman Roviri East Norwalk, Conn. Appl. No. 822,270 Filed May 6, 1969 Patented July 13,1971 Assignee Ivanhoe Research Corporation New York, NY.

APPARATUS FOR AUTOMATICALLY DIFFERENTIATING AND FEEDING FLEXIBLE WORKPIECES ONE AT A TIME FROM A STACK 9 Claims, 9 Drawing Figs.

u.s.c| .t 221/36, 221/1.221/56,221/63.22l/2l1,221/230 Int.Cl B65h1/08, B65h 3/08. 865g 59/04 FieldofSearch .0 22l/1,36,

I 56 1 References Cited UNITED STATES PATENTS 3,322,301 5/1967 Bliss 221/1 2,828,596 4/1958 Dowty etal.... 221/211X 2,816,760 12/1957 Seragnoli 1 v I 221/211 X 2,074,815 3/1937 Tevanderet a1. 221/211 X 1,357,071 10/1920 Matthews 1 .1 221/230 1,204,188 11/1916 Pye 221/211 X Primary Examiner Leonard Summer Att0rney Bryan, ParmeleeJohnson & Bollinger ABSTRACT: A hopper holds a stack of workpieces which are fed to a discharge mouth at one end of the hopper by intermittent pressure feed means, a movable suction head located near the discharge mouth, through which suction is applied, withdraws the end pieces, one at a time, from the stack away from the discharge mouth (at time intervals) during cycles of operation when the intermittent feed means relieves the pressure applied to the stack.

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P -MMZQEIL Q, WIVM APPARATUS FOR AUTOMATICALLY DIFFERENTIATING AND FEEDING FLEXIBLE WORKPIECES ONE AT A TIME FROM A STACK This invention provides an apparatus for differentiating and feeding flexible, semiporous workpieces one at a time from the end ofa stack. Automation of the separation of such workpieces for products which utilize semiporous materials is mechanically accomplished rapidly and reliably. The term flexible, semiporous workpieces is intended to include workpieces of densely woven cloth, canvas, and similar flexible, semiporous material, which are utilized in the manufacture of tennis and boating shoes, sporting equipment, protective articles of clothing, and similar products.

Many problems have arisen in the past when trying to separate such semiporous workpieces one at a time from a stack. It has been difficult to provide a method and/or apparatus utilizing suction which will differentiate pieces from a stack one at a time both rapidly and reliably, because the semiporous material allows the suction airflow to pass through more than one workpiece such that two workpieces may be picked off at once. This invention eliminates such doubles."

It is an advantage of the present invention that workpieces of semiporous material can be individually differentiated from a stack both rapidly and reliably by suction.

Another advantage of the present invention is that the workpieces being differentiated are differentiated from one end of a storage means or hopper permitting additional workpieces to be added to the storage means without interrupting or interferring with the differentiating process or apparatus functioning at the other end of the hopper or discharge mouth.

The present invention provides an apparatus for automatically separating and feeding flexible, semiporous workpieces, one-at-a-time, from the end of a stack of workpieces. Refillable hopper means holds a stack of workpieces, and the workpieces are fed to a discharge mouth at the end of the hopper means by an intermittent feed means. The intermittent feed means advances the stack toward the mouth where the end workpiece engages retaining means located at the discharge mouth of the hopper means.

Intermittently actuated feed means cyclically advances the workpieces of the stack toward the mouth of the hopper while alternately relieving the pressure on the end piece of the stack against the retaining means at time intervals during successive cycles of operation.

Movable suction head is reciprocally driven in a cyclic relationship with the feed means. Suction through the movable suction head is applied and withdrawn in phase relationship with the position of the suction head, with respect to the discharge mouth of the hopper. When the suction head means, within its cycle, approaches near the discharge mouth, suction is applied and drawn through the suction head means for securing the end workpiece in the stack and for removing such secured workpiece from the stack through the discharge mouth of the hopper as the head means reciprocates from the discharge mouth of the hopper. After the suction head has fully withdrawn the secured workpiece from the discharge mouth of the hopper, suction is withdrawn from the suction head or removed and the workpiece is discharged by the suction head as the suction head continues through the absenceof-suction phase of its cycle, but before approaching the suction phase ofthe cycle.

Relief of pressure on the end workpiece in the stack and application of suction through the mouth of the suction head is synchronized with the reciprocating movement of the suction head such that when the suction head is approaching the discharge mouth ofthe hopper, pressure on the end workpiece of the stack of workpieces in the hopper is progressively relieved and when the suction head has progressed toward the discharge mouth, a predetermined amount in its approach to the discharge mouth, suction to or through the suction head is progressively increased. Essentially, during the cyclic movement of the suction head, the amount of suction applied to or through the suction head increases as the distance between the mouth of the suction head and the discharge mouth of the hopper decreases and the amount of pressure applied to the end workpiece in the stack of workpieces in the hopper decreases as the distance between the mouth of the suction head and the discharge mouth of the hopper decreases.

In this specification and in the accompanying drawings are shown and described methods and apparatus for automatically separating and feeding flexible workpieces one at a time from a stack. It is to be understood that these illustrative examples are not intended to be exhaustive nor limiting of the present invention, but on the contrary are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the manner of applying the invention in practical use, so that they will understand how to modify and adapt it in various forms, each as may be best suited to the conditions of a particular use.

The various objects, aspects, and advantages of this invention will be more fully understood from a consideration of the following specification in conjunction with the accompanying drawings:

FIG. I is a perspective view of apparatus embodying and for practicing the present invention.

FIG. 2 is a front view of the apparatus of FIG. 1.

FIG. 3 is an end view showing the movable suction head positioned near the discharge mouth of the hopper, about to withdraw the end piece from the stack.

FIGS. 4, 5 and 6 are rear views showing various positions of the operating parts at successive periods during a cycle of operation.

FIG. 7 is a perspective view similar to FIG. 1 and showing an alternative embodiment.

FIG. 8 is a crosssectional view taken along the plane A-A in FIG. 7, shown in enlarged scale, illustrating the suction control at a sequence of operating positions.

FIG. 9 shows a further embodiment in which a belt aids in feeding the stack forward.

As shown in FIG. 1, hopper means 2 mounted on a frame 4 is adapted to hold a stack 6 of workpieces to be fed to the discharge station or mouth 8 of the hopper means. Retaining means are located at the mouth 8 to retain the stack 6 within the hopper 2. The retaining means are shown as including retaining clips 10 and spaced, parallel retainer rolls 12.

In order to advance the stack 6 toward the mouth 8, there is provided feed means located within the hopper 2 serving to apply pressure to the stack such that the end workpiece 14 engages the retainer means 10 and 12. The feed means includes a pressure plate 16 and rolling member such as a ball or cylindrical weight 18 which may be rotatably connected to the pressure plate so that the roller weight 18 can roll longitudinally in the hopper 2 for urging the plate 16 intermittently toward the stack to exert pressure against the workpieces of the stack.

As shown in FIG. 4, the hopper means 2 is cyclically inclined downwardly toward the mouth, thus causing the roller weight 18 to roll toward the mouth 8 for causing the pressure plate 16 to apply feed pressure 19 to the stack. As shown in FIG. 6, the hopper means is cyclically lowered toward a horizontal position for relieving the feed pressure.

The actuation means for intermittently actuating the feed means 16, 18 includes a motor 20 connected through gears 22, see FIGS. 4, 5 and 6, to provide a specific synchronized relationship between the motion of the hopper, feed means and suction head means, as explained in detail further below.

As seen in FIG. 1, the movable suction head 24 has suction applied to it as it moves toward the discharge mouth 8. The feed means l6, l8 relieves the pressure from the stack 6 as the suction head approaches the discharge mouth 8. The rapid inflow of air into the suction head 24 withdraws a localized region of the end workpiece 14 away from next workpiece creating a channel therebehind extending out to the edge so as to allow air to enter freely into the space thus created between this localized region and-the next workpiece. The mouth 60 of the suction head 24 includes two protruding lips 25 at top and bottom with recesses on either side, and this twin lip configuration aids in withdrawing and separating the localized region of the end workpiece from the next workpiece by deforming or curving the localized region in conformance with the recesses of the mouth of the head to provide a channel extendlng out to the edge of the workpiece providing clearance space for air to enter lreely between the end workpiece 1 sand the next one. Thus, atmospheric pressure is now applied to the reverse side of the end workpiece 14 so that it can be completely and singularly withdrawn from the retainer means 10 and 12. Y

The top of the approach phase of the cycle of the suction head 24 most closely adjacent to the discharge mouth 8 may be referred to as the start of first position in the cycle. in this position suction applied to or through the head is maximum and pressure applied to the end workpiece of the stack is minimal.

The localized region of the end workpiece is drawn by the suction against the movable suction head 24 distorting the workpiece and creating a space or channel between the end workpiece in the stack and the adjacent workpiece; Thus air is able to pass between the workpiece being removed, i.e. the one drawn against the suction head 24, and the next workpiece in the stack, without passing through the next workpiece in the stack, according removal of one workpiece from the stack at one time. The suction solely applied to the localized region of the end workpiece is sufficient to overcome the friction hold of the retaining clips 10 and the retainer rollers 12. Thus, positive differentiation of one, the end, workpiece from a stack of workpieces is achieved in spite of the semiporous nature of the material of the workpiece.

The retaining clips 10 located at the discharge mouth 8 and the spaced parallel retainer rollers 12 function to keep the flexible, semiporous workpieces of the stack in the hopper 2 unless acted upon by sufficient force. Specifically, the retaining clips 10 are preferably spring clips which hold the end workpiece when it is part of the stack and snap in position to hold the next workpiece after the end workpiece is removed from under the/clips by the movable suction head 24. The retainer rollers l2 engage the end workpiece near its opposite ends. The retaining clips l and the retainer posts or rollers 12 cooperate to hold the stack in the hopper and particularly permit access to the end workpiece by the suction head 24 while retaining the stack in.the hopper. The retainer rollersor posts 12 ofi'er, very little friction against the end workpiece when it is drawn by the suction head 24 out of the discharge mouth of hopper 2. The retainer rollers or posts 12 may be mounted to be freely rotatable, as indicated by the insert in FIG. 3.

The relative sequence of positions of the hopper 2, feed means and suction head can be most clearly seen in FIGS. 4, and 6. The motor 20 is energized and a positive drive belt 2e (see FIGS. 1 and 2) drives the pair of meshing gears 22 of the same diameter which synchronize the motion of the hopper 2 and the movable suction head 24 in a one-tonne cycle relationship. in FIG. 4, the movable suction head 24 is in its second or release position. in this position, the vacuum is fully interrupted by means of a cam 28 which activates a microswitch 30 and shuts a solenoid valve .31 (H08. 1 and 2) controlling the vacuum applied to the movable suction head 24. FIGS. 4--6 schematically illustrate the sequence of operation of this solenoid valve in moving from full open to full shut position. When the movable suction head 24 is in second position the hopper 2 is swung up slightly so that its discharge mouth 8 is below the remainder of the hopper 2. This inclined position of the hopper 2 causes gravity to act on the feed means, the plate 16 and roller 18, causing the plate 16 to press against the stack 6 under the force of the weight of the roller [8. As a result of this pressure the stack 6 is advanced along the hopper 2'and the next piece is pressed against the retaining clips and retainer rollers 12. in some instances. since gravity will also set upon the melt. the melt alone may have with elem weight to move or advance the workpieces toward the discharge mouth in conjunction with the rise and fall of the hopper.

As the gears 22 continue to rotate the hopper 2 begins to swing back down toward a more horizontal position in relation to the frame 4. This downward movement causes the feed means, plate 16 and roller 18, to progressively relieve the feed pressure applied to the stack, as shown in FIG. 6. in fact, the feed means 16. 18 may briefly move away from the stack, releasing completely the pressure applied to the stack 6 through the plate 16. Simultaneously, the movable suction head 24 removes the end workpiece from the discharge mouth 8, see FIG. 6.

The sequence of operations is as follows: as the hopper 2 to cause movable suction head 24 move nearer the first position as shown in FIG. 6, the cam 28 which is mounted on the pivot axis of the suction head so as to rotate with the movable suction head 24, progressively opens the solenoid valve 31, applying an increasing vacuum to the movable suction head 24. At this time in the'cycle of operation, the feed means l6, 18 has moved slightly away from the stack 6 and has relieved the pressure applied to the stack 6. The movable suction head 24 at the top of its approach phase has moved sufficiently close to the discharge mouth 8, see FIG. 1, to cause the localized region of the end workpiece 1 4 of material to be drawn against the movable suction head 24 by the suction applied to the suction head, as described in detail above. The head 24 then moves away from the discharge mouth of the hopper completely separating and withdrawing the end workpiece from the stack as described above. As the head 24 continues to move toward its second position, the cam 28 opens the microswitch 30 to interrupt the vacuum in the movable suction head 24 so that the withdrawn workpiece is discharged or released. This cycle is repeated until all the flexible semiporous workpieces comprising the stack 6 are in dividually differentiated from the stack, one at a time.

Referring to FIGS. 2, 3, and 4, the hopper 2 is shaped to accommodate a stack 6 of flexible semiporous workpieces. This hopper is generally U-shaped in cross section to accommodate the largest size of the workpieces intended to be handled. The hopper includes a pair of upstanding sidewalls and a raised deck region 61. In this illustrative example, the workpieces are of canvas in a shape to form the top portion of acanvas athletic shoe. it is an advantage of this invention that it enables a wide range of sizes of similar workpieces tobe handled without changing the hopper 2. This is accomplished by placing the respective stacks of workpieces of different sizes one behind the other inthesame hopper 2. The method and apparatus as shown automatically proceedfrom workpiece to workpiece without interruption in the sequential cycles, in spite of changes in the size of the piece. This size change occurs when the last piece of one stack has been removed from the hopper and the first piece of the next stack of different size is being removed. The hopper 2 is plvotully attached to the frame by means of a bracket 32 is raised and lowered by a first rod 34 driven by first gear 36 oithe pair 22.

The motor 20 is mounted on the frame 4 and when energized it rotates the first gear 36 by means of the drive belt 26. The rotating belt 26 drives the first gear 36 and the first connecting rod 34 extending between and pivotally attached to the hopper 2 and to a crank arm 38 connected to the first gear 36. This arrangement causes the first connecting rod to follow the rotation of the first gear 36 imparting a rocking motion to the hopper 2.

The second gear 40 of the pair 22 meshes with the first gear 36 and thus rotates in synchronization therewith, but in the opposite direction from the rotation of the first gear 36. A second connecting rod 42 is pivotally attached to the suction head body 44 and to a second crank arm 46 driven by gear 40. This arrangement causes the second rod 42 to follow the rotation of the second gear 40 imparting a rocking motion to the suction head body 44.

The suction head body 44 is pivotally attached to the frame 4 tJnough u hollow rotatable tubular shaft 8 closed at one on The tubular shaft 48 has a vacuum hose 50 connected to its open end 52 to provide suction through the body 44 to the movable suction head 24 when the solenoid valve 31 is open. The cam 28 is attached to the closed end 54 of the rotating tubular shaft 48 and rocks back and forth therewith so to activate the microswitch 30 which controls the solenoid valve 31.

As the movable suction head 24 swings way from the discharge mouth 8 of the hopper 2 carrying a single flexible semiporous workpiece with it, the cam 28 engages the microswitch 30 so as to release the workpiece from the movable suction head 24. The released workpiece 56 (FlG. l) is deposited on a chute 58 and the cycle is repeated until all workpieces of the stack 6 are differentiated one at a time. A sloping shelf 62 associated with the chute 58 aids in releasing the separated workpiece from the suction head 24.

FIGS. 7 and 8 show an alternative embodiment of the invention in which the suction is interrupted by means of a shutter valve (FIG. 8) at the periods when the suction head 24 swings over into its second (release) position. The shutter valve 64 is used in lieu of the solenoid valve 3i (FIG. 1), and it is located at the junction between the hose 50 and the end 52 of the hollow shaft 48. This shutter valve 64 includes a pair of sectorshaped stationary blades 66 which are mounted within the stationary coupling 68 at the end of the hose 50. This coupling 68 is adjacent to the open end of the shaft 48. Cooperating with these stationary blades are a pair of movable blades 70 which are connected to the hollow shaft 48 so as to move therewith, thus interrupting the suction once during each cycle when the suction head 24 is in its second position.

As shown in FIG. 9, a feed belt 72 may be incorporated in the bottom of the hopper 2 in either of the foregoing embodiments for the purpose of aiding in feeding the stack 6 toward the discharge mouth 8 of the hopper 2. This belt 72 passes around a pair of rollers 74 and 75 and is intermittently hitched forward by a ratchet mechanism 76 which is actuated by the rocking motion of the hopper 2. The axis of roller 75 is located near the discharge end of the hopper 2, and a ratchet wheel 78 is attached to this roller. A spring-biased pawl 80 engages this ratchet wheel. In most applications, the roller weight 18 and pusher plate 16 are quite adequate to feed the stack forward when the hopper is inclined downwardly at an angle during each cycle as shown in FIG. 4. If it is desired to use a lesser angle of inclination of the hopper 2 during each cycle, then the feed belt 72 may be used. The upper surface of this belt is vof slippery plastic such that the force of the end piece 14 against the retaining means l0, 12 at the discharge mouth 8 is controlled by the pusher plate 16 and weight 18 and not by the intermittent movement of the belt 72.

The terms and expressions which have been used in the specification are used in a descriptive and not a limiting sense, and there is no intention of excluding equivalents of the invention described and claimed.

lclaim:

1. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces comprising rocking hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth and being mounted to rock up and down for inclining said hopper means downwardly toward said discharge mouth, retaining means at said mouth for retaining the stack within said hopper means, feed means for advancing the stack toward said mouth when the hopper is inclined downwardly toward the mouth with the end workpiece engaging against said retaining means, said feed means relieving the pressure of the end piece against said delivering means when the hopper is rocked in the opposite direction, movable suction head means, drive means for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive means moving said suction head to said first position at times when said hopper has been rocked in the opposite direction and the pressure of the end piece against said retaining means has been relieved, means for providing a suction in said suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.

2. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces comprising hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth and being adapted to rock up and down for inclining said hopper means downwardly toward said discharge mouth, retaining means at said mouth for retaining the stack within said hopper means, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, said feed means being a roller weight rotatably connected to a pressure plate located within said hopper means behind said stack so that said weight and plate intermittently apply pressure to said stack when said hopper is inclined downwardly toward said mouth, intermittent actuation means causing said hopper to rock up-and down for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure of the end piece against said retaining means, movable suction head means, drive means for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive means, moving said suction head to said first position at times when said actuation means has relieved the pressure of the end piece against said retaining means, means for providing a suction in said suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.

3. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces as claimed in claim 2 in'which said intermittent actuation means included a drive motor, a pair of gears of equal size driven by said motor, a first crank arm and connecting rod driven by one of said gears and connected to said hopper means for rocking the hopper means and a second crank arm and connecting rod driven'by the other of said gears and connected to said suction head means foroperating said suction head means in synchronism with the rocking movement of said hopper means.

4. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces comprising hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth, retaining means at said mouth for retaining the stack within said hopper means, said retaining ,means including retainers adapted to engage the end workpiece in said stack and spaced parallel rolls engaging opposite ends of said end workpiece in the stack, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, intermittent actuation'means for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure ofthe end piece against said retaining means, movable suction head means, drive means for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive meansmoving said suction head-to said first position at times when said actuatiori. means has relieved the pressure of the end piece against said retaining means, means for providing a suction insaid suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.

5. Apparatus for automatically differentiating and feeding flexible semiporous workpieces oneat-a-time from the end of a stack of such workpieces as claimed in claim 4 wherein said suction head in said first position is located near said retainers in said mouth for withdrawing said end workpiece from said retainers while the ends remain restrained by said rolls.

6. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces as claimed in claim 4 wherein said hopper means is generally U-shaped to accommodate workpieces of different sizes and said hopper means is further adapted to be rockable under influence of said intermittent actuation means, said feed means being a roller weight and plate adopted to roll along the bottom of said U-shaped hopper.

7. Apparatus for automatically differentiating and feeding flexible semiporous first position one-at-a-time position being the end of a stack of such workpieces comprising hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth, retaining means at said mouth for-retaining the stack within said hopper means, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, intermittent actuation means for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure of the end piece against said retaining means, movable suction head means, said suction head means including a pair of spaced lips defining recesses therebetween for withdrawing a localized region of the end workpiece away from the next workpiece to admit air freely to the reverse side of said end workpiece, drive means for moving said suction head means between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive means moving said suction head to said first position at times when said actuation means has relieved the pressure of the end piece against said retaining means, means for providing a suction in said suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.

containing means Apparatus for automatically differentiating flexible semiporous workpieces one-ata-time from the end of a stack of such workpieces comprising a hopper for holding a stack of said workpieces, said hopper having'a discharge mouth with retain means at said mouth for retaining the stack within said hopper, said retaining means comprising spaced parallel retainer rolls attached to said hopper at said discharge mouth and retaining elements attached to said hopper at said discharge mouth, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, said feed means comprising a movable roller attached to a pressure plate located behind said stack so that said plate can intermittently apply pressure to said stack, intermittent actuation means for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure of the end piece against said retaining means, said intermittent actuation means including a motor which drives said hopper to provide a rocking motion to said hopper when said motor is energized, a movable suction head, said suction head comprising a pair of lips having a pair of recesses therebetween to withdraw a localized region of the end piece from the stack at said discharge mouth, said motor also driving said suction head when said motor is energized for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a released position spaced from said first position, said drive means moving said suction head to said first position at times when said actuation means has relieved the pressure of said pressure plate from the stack, means for providing a suction in said suction head when in said first position for withdrawinlg the end piece from said retaining means, and means for re easing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.

said swinging Apparatus for automatically differentiating flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces as claimed in claim 8 wherein said releasing means includes a cam operatively associated with said swinging suction head to move therewith and adapted to actuate a switch, a solenoid valve electronically connected to said switch, said solenoid valve interrupting said suction providing means as said cam actuates said switch when said suction head is moving into said second position. 

1. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces comprising rocking hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth and being mounted to rock up and down for inclining said hopper means downwardly toward said discharge mouth, retaining means at said mouth for retaining the stack within said hopper means, feed means for advancing the stack toward said mouth when the hopper is inclined downwardly toward the mouth with the end workpiece engaging against said retaining means, said feed means relieving the pressure of the end piece against said delivering means when the hopper is rocked in the opposite direction, movable suction head means, drive means for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive means moving said suction head to said first position at times when said hopper has been rocked in the opposite direction and the pressure of the end piece against said retaining means has been relieved, means for providing a suction in said suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.
 2. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces comprising hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth and being adapted to rock up and down for inclining said hopper means downwardly toward said discharge mouth, retaining means at said mouth for retaining the stack within said hopper means, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, said feed means being a roller weight rotatably connected to a pressure plate located within said hopper means behind said stack so that said weight and plate intermittently apply pressure to said stack when said hopper is inclined downwardly toward said mouth, intermittent actuation means causing said hopper to rock up and down for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure of the end piece against said retaining means, movable suction head means, drive means for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive means moving said suction head to said first position at times when said actuation means has relieved the pressure of the end piece against said retaining means, means for providing a suctIon in said suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.
 3. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces as claimed in claim 2 in which said intermittent actuation means included a drive motor, a pair of gears of equal size driven by said motor, a first crank arm and connecting rod driven by one of said gears and connected to said hopper means for rocking the hopper means and a second crank arm and connecting rod driven by the other of said gears and connected to said suction head means for operating said suction head means in synchronism with the rocking movement of said hopper means.
 4. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces comprising hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth, retaining means at said mouth for retaining the stack within said hopper means, said retaining means including retainers adapted to engage the end workpiece in said stack and spaced parallel rolls engaging opposite ends of said end workpiece in the stack, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, intermittent actuation means for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure of the end piece against said retaining means, movable suction head means, drive means for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive means moving said suction head to said first position at times when said actuation means has relieved the pressure of the end piece against said retaining means, means for providing a suction in said suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position.
 5. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces as claimed in claim 4 wherein said suction head in said first position is located near said retainers in said mouth for withdrawing said end workpiece from said retainers while the ends remain restrained by said rolls.
 6. Apparatus for automatically differentiating and feeding flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces as claimed in claim 4 wherein said hopper means is generally U-shaped to accommodate workpieces of different sizes and said hopper means is further adapted to be rockable under influence of said intermittent actuation means, said feed means being a roller weight and plate adopted to roll along the bottom of said U-shaped hopper.
 7. Apparatus for automatically differentiating and feeding flexible semiporous first position one-at-a-time position being the end of a stack of such workpieces comprising hopper means for holding a stack of such workpieces, said hopper means having a discharge mouth, retaining means at said mouth for retaining the stack within said hopper means, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, intermittent actuation means for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure of the end piece against said retaining means, movable suction head means, said suction head means iNcluding a pair of spaced lips defining recesses therebetween for withdrawing a localized region of the end workpiece away from the next workpiece to admit air freely to the reverse side of said end workpiece, drive means for moving said suction head means between first and second positions, said first position being near said discharge mouth and said second position being a release position spaced from said first position, said drive means moving said suction head to said first position at times when said actuation means has relieved the pressure of the end piece against said retaining means, means for providing a suction in said suction head means when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position. containing means Apparatus for automatically differentiating flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces comprising a hopper for holding a stack of said workpieces, said hopper having a discharge mouth with retain means at said mouth for retaining the stack within said hopper, said retaining means comprising spaced parallel retainer rolls attached to said hopper at said discharge mouth and retaining elements attached to said hopper at said discharge mouth, feed means for advancing the stack toward said mouth with the end workpiece engaging against said retaining means, said feed means comprising a movable roller attached to a pressure plate located behind said stack so that said plate can intermittently apply pressure to said stack, intermittent actuation means for intermittently actuating said feed means to advance the stack toward said mouth and to relieve the pressure of the end piece against said retaining means, said intermittent actuation means including a motor which drives said hopper to provide a rocking motion to said hopper when said motor is energized, a movable suction head, said suction head comprising a pair of lips having a pair of recesses therebetween to withdraw a localized region of the end piece from the stack at said discharge mouth, said motor also driving said suction head when said motor is energized for moving said suction head between first and second positions, said first position being near said discharge mouth and said second position being a released position spaced from said first position, said drive means moving said suction head to said first position at times when said actuation means has relieved the pressure of said pressure plate from the stack, means for providing a suction in said suction head when in said first position for withdrawing the end piece from said retaining means, and means for releasing the withdrawn piece from said suction head when said suction head is in said second position for delivering the withdrawn piece at said second position. said swinging Apparatus for automatically differentiating flexible semiporous workpieces one-at-a-time from the end of a stack of such workpieces as claimed in claim 8 wherein said releasing means includes a cam operatively associated with said swinging suction head to move therewith and adapted to actuate a switch, a solenoid valve electronically connected to said switch, said solenoid valve interrupting said suction providing means as said cam actuates said switch when said suction head is moving into said second position. 